Performance, exhaust emission and combustion of ethanol–diesel–compressed natural gas dual-fuel compression-ignition engine: a trade-off study

The present work investigates the effect of ethanol addition in pilot fuel on performance, combustion and emission of a partially modified dual-fuel compression-ignition engine under different compressed natural gas strategies. The ethanol is mixed in diesel with 5 and 10% (v/v) proportions, whereas natural gas was injected in the intake manifold at three different flowrates, i.e., 0.02 kg/h, 0.2 kg/h and 0.22 kg/h. It is observed that brake thermal efficiency is increased by 22.57% with 0.02 kg/h gas flow rate at 1.4 bar BMEP. The emissions of oxides of nitrogen and carbon monoxide are also observed to be lower by 26.41% and 8.17% at the same condition, respectively. To this end, a multi-objective particle swarm optimization technique is utilized to obtain Pareto front of the optimal results. Further, a multi-attribute decision-making-based technique for order preference by similarity to ideal solution methodology is incorporated to find the optimal dual-fuel engine operating conditions. The optimization algorithm showed optimal operating conditions to be 4.17 bar brake mean effective pressure, 0.019 kg/h compressed natural gas share and 10% (v/v) ethanol share, where 33.43% brake thermal efficiency, 0.808 g/kWh of cumulated oxides of nitrogen and unburned hydrocarbon, 0.091 g/kWh of particulate matter and 0.969 g/kWh of carbon monoxide is attainable. Actual experiments conducted at the optimal operating conditions showed 0.20% lower brake thermal efficiency, 2.47% higher cumulated oxides of nitrogen and unburned hydrocarbon, 0.70% higher particulate matter and 15.49% lower carbon monoxide emission as compared to the optimized values.